Use powershell to do an export of a running Hyper-V Guest.

Export a live VM using Powershell

You can do lots of things with powershell in hyper-v one of the great ones is automating an export of your virtual machines.

To do that you use a very simple powershell script

Export-VM -Name $VMNAME -Path $PATH

Now you can use this in a loop script to export your VMs to a network storage location, external drive, what ever you need.